1. Field of the Invention
The invention relates to a method for jointing the cutting edge of at least one cutting blade of a rotating tool wherein a radial advancing movement is carried out between the tool and at least one straight jointing stone whose effective joint area is longer than the cutting edge.
2. Description of the Related Art
When peripherally milling workpieces, a groove pattern comprised of grooves having a certain spacing between neighboring grooves is generated on the workpiece surface. The groove pattern depends on the machining parameters such as rotational speed of the tool, number of cutting edges of the tool, and the advancing speed of the tool. The spacing of neighboring grooves is an essential quality criterion for the surface of the workpiece. A high-quality workpiece surface is characterized by a uniform groove pattern whose groove spacing is between approximately 1 mm and 2 mm.
When employing conventional tools and conventional tool clamping systems, only one cutting edge will be imprinted on the workpiece surface as a result of the tolerances with respect to the cutting circle of the different cutting edges of the tool and the concentricity of the clamped tool. The cutting circle is the circle described by the rotating cutting edges, respectively. In this way, the achievable advancing speed of the tool for a high-quality milling action depends only on the rotational speed of the tool and, like the rotational speed of the tool, is thus limited by the configuration or construction of the tool. In practice, workpiece advancing speeds of approximately 20 m/min. result.
In order to be able to achieve higher advancing speeds (for example, >20 m/min) which are proportional to the number of cutting edges of the tool, all of the cutting edges of the cutting blades of the tool must imprint uniformly on the surface of the workpiece to be machined. In order to achieve this, the cutting edges of the cutting blades are jointed within the machine, i.e., the cutting edges, when the tool is rotating, are adjusted to be positioned on a uniform cutting circle of the rotating edges by advancing a jointing stone and subjected to whetting or grinding. A prerequisite for this is that the tools themselves are already very precisely ground to run true and that the tool clamping system has only minimal tolerances with respect to concentricity. In practice, the tools are centrally clamped by means of hydraulic clamping systems for this purpose. Also, the tools are clamped with cone clamping systems (positive taper lock system).
When carrying out jointing, the cutting edge of the cutting blade is radially ground, i.e., at a clearance angle of 0°. However, this is possible only to a certain degree because otherwise the cutting edge would perform a pushing action and thus reduce the machining quality. In practice, so-called jointing bezel widths of a maximum of 0.7 mm are permissible. In order to be able to carry out as many jointing processes before reaching this maximum jointing bezel width, the aforementioned conditions must be provided. Otherwise, a great portion of the possible jointing bezel width will already be used during the first jointing process with which initially the cutting edges of all cutting blades of the tool are aligned on a uniform cutting circle.
After grinding and insertion of the tools with the clamped cutting blades for the first jointing process, the jointing stone is radially advanced step-by-step until all cutting blades are brought into contact with the jointing stone, i.e., all cutting blades are jointed. Subsequently, approximately 1.5 mm to 2/100 mm advancing strokes are radially performed for each jointing process. When the maximum jointing bezel width has been reached, the tools with the clamped cutting blades are removed from the machine and the cutting blades are then finish-ground in a grinding machine.
A principal distinction is made between straight jointing and profile jointing. In the case of straight jointing (FIG. 6) of straight non-profiled cutting blades 3, a jointing stone 31 in the form of a pin is radially advanced and subsequently moved axis-parallel in order to joint the cutting edges 9 of the cutting blades 3 across their entire length. A disadvantage is that relatively small jointing stones 31 will wear relatively quickly and, in an extreme situation, the jointing result will be a conically tapering cutting blade 3.
When profile jointing, the jointing stone is provided with the negative contour of the cutting edge of the cutting blade and is advanced only in a radial direction.
In the case of straight jointing, it is also known to employ a straight jointing stone whose length is somewhat greater than the jointing cutting edge of the cutting blade. This jointing stone is advanced only radially. A disadvantage of this straight jointing process is that, for example, a nick or notch within the jointing stone will be directly transmitted onto the cutting edge of the cutting blade and will cause marks on the cutting edge. This disadvantage must be accepted for profile jointing; however, in this application, the effect is not as strong because of the already profiled cutting edge configuration.
As a result of the different type of action, the straight and profile jointing devices are configured constructively differently and are either mounted alternatively correlated with the respective spindle of the machine or, depending on the tool, are employed alternatively.